Here is a step by step instructions to use authentication in your template.

Authentication With Firebase

To add Firebase to your app, you’ll need a Firebase project, Firebase SDK and a short snippet of initialization code that has a few details about your project.

1. Create a Firebase project in the Firebase console, if you don’t already have one.
   1. If you already have an existing Google project associated with your app, click Import Google Project. Otherwise, click Create New Project.
   2. If you already have apps in your project, click Add Another App from the project overview page.
2. Click Add Firebase to your web app.
3. Copy the initialization code snippet, we will use this code in the next step.
4. Open the file src->firebase->index.js and search for the const firebaseconfig & paste the code inside it:

Removing Firebase Authentication

If you want to remove the firebase authentication from your existing template then please follow this link Completely Remove Firebase From Template and follow the steps given.